1. Field of the Invention
The present invention relates to a high speed optical switch and the use of such switch to form a time division optical demultiplexer and, more particularly, to a high speed optical switch comprising a layer of nonlinear material and a layer of linear material forming a nonlinear interface at the boundary of the two materials, and a selectively energizable control light beam directed at the nonlinear interface. An input data beam propagating in the linear material with a predetermined intensity and angle of incidence when impinging the nonlinear interface is totally reflected in the absence of the control light beam and a portion thereof is formed into a self-focused beam in the nonlinear material in the presence of the control light beam. Multiple switches can be arranged in sequence to form a time division optical demultiplexer.
2. Description of the Prior Art
Optical switching devices have been of considerable interest for use in laser and optical communication systems to enable light beams to be switched along various paths and for performing multiplexing and demultiplexing function. An optical switching device is disclosed in U.S. Pat. No. 4,190,811 issued to A. J. Alcock et al on Feb. 26, 1980. There, apparatus is described wherein a signal beam from a first laser is directed at a surface of a semiconductor at Brewster's angle and is transmitted through the semiconductor to a first utilization device. A control beam of sufficiently high intensity from a second laser is also selectively directed at the semiconductor surface and when such control beam is present, free carriers are created in the semiconductor to cause total reflection of the signal beam.
The article "Optical Bistability at a Nonlinear Interface" by P. W. Smith et al in Applied Physics Letters, Vol. 35, No. 11, Dec. 1, 1979 at pages 846-848 describes an optical element based on the intensity dependent reflectivity of an interface between a linear and a nonlinear medium. A low intensity beam with an angle of incidence less than the critical angle is directed at the interface and is totally reflected. However, at some threshold input intensity a sudden switch in state occurs to produce both a reflected beam portion and a beam portion which is transmitted in the nonlinear medium.
The article "Surface Wave at a Nonlinear Interface" by W. J. Tomlinson in Optics Letters, Vol. 5, No. 7, July 1980 at pages 323-325 discloses that a nonlinear interface is intensity sensitive and it is possible to excite a surface wave that propagates along the interface with a constant shape and intensity for possible detection at the edge of the interface.
U.S. Pat. No. 4,244,145 issued to K. Nosu et al on Jan. 6, 1981 discloses a wavelength division optical multiplexer and demultiplexer wherein each of one or more optical filters are used to pass a predetermined separate bandwidth of a wider band multiplexed signal and reflect all other frequencies.
The problem remaining in the prior art is to provide a high speed switch which can operate with subpicosecond switching times that is easy to construct and capable of being used to form a time division optical demultiplexer.